In the present crime ridden environment a surveillance system is not a luxury but a necessity.
Having a few additional eyes and ears enables you to be alert to any risks in your environment. It gives you the opportunity to take appropriate action to prevent any threats to your well being.
Present technology gives you the opportunity to view your environment from the comfort of your house, office or from anywhere in the world. Furthermore a suitable system can detect movement in the area viewed, raise alarm giving you the opportunity to take necessary action.
The basics, be it a start up or a more elaborate system, is the same and this guide will get you started on the right track.
Systems range from a basic camera and TV,computer based systems to stand alone systems. You do not require the latest greatest most expensive to ensure adequate viewing.
In any system one consideration stands out “clear vision” and by focusing on this you will be on your way in obtaining a good system.
Electrical current powers the system - monitor and the cameras. AC power is converted to DC power normally up to 12 volts.
Power outlets are required near cameras and the monitor, the nearer to the camera the better. Sometimes batteries are used to power cameras but they do not last very long.
Available power outlets for DC converter power supplies
Camera/s
Monitor
Cable
Connectors
Integrated DVR system to view from any where and record the multiple camera images plus an integrated alarm system.
Cameras are the most important part of any system. It is made up of a lens, an image sensor, infrared lights, IR, to enable viewing in darkness and sometimes a microphone to pick up sounds in the vicinity of the camera.
If the surrounds viewed are sufficiently lit IR light will not be necessary but in the outdoors during night time external lighting is seldom sufficient. Installing sufficient lighting could be expensive and your power consumption will increase.
Many cameras are available with different specifications. Day or night, low light, infrared, black/white, colour, indoor, outdoor, and weather proof. For security purposes we will focus on cameras that enable viewing in very low light or in the dark. Generally monochrome B&W cameras are clearer but we suggest colour as identifying colours would be beneficial. Many colour cameras changes to monochrome in darkness.
Light illuminates objects. A certain portion of this light is reflected back to the camera through the lens to the image sensor where a charge is generated and converted to a video signal.
The intensity of the reflected light depends on the surrounds and objects. Generally brighter coloured surrounds or objects reflect more light and the image viewed would be clearer. White surrounds as snow reflects back 90% of light, grass 40%, concrete 25%, black objects 5%.
Clearer viewing therefore not only depends on the intensity of the lighting but also on the colour of surrounds and objects viewed. The darker or less intensity of reflected light means you would require more illumination light - more lighting. During the same lighting conditions at night a white object would be viewed clearly and a black object perhaps not at all.
Light required by the camera to enable viewing is measured by the standard measure of luminescence LUX. It can be defined as how much light would strike a similar sphere of one meter in diameter.
The higher the LUX the brighter the light or illumination required.
For cameras, the lower the lux required the better; 0 lux means that the camera can enable viewing in darkness.
Infrared enabled cameras enable viewing in total darkness.
Infrared Light or IR is a frequency of light which is invisible to the human eye but detectable by monochrome cameras. The more lights in a camera the clearer and the further images are view-able in the dark. Usually colour cameras during darkness change to black and white images but many latest cameras have image sensor technology to enable the viewing of images in colour in the dark.
Clear images are essential, choose well after careful consideration.
Light is reflected through the lens of the camera to the image sensor, either CMOS or CCD based, which process the image.
CMOS image-rs convert charge to voltage inside each pixel. It uses a charged metal surface to detect light and create a video image on one pixel.
CCD moves a photo generated charge from pixel to pixel and converts it to voltage at an output mode, a solid-state semiconductor element which uses thousands of tiny pixel elements to accept light and transform that into an image.
CCD technology is considered better and used by the medical profession but major strides have been made in CMOS technology. Either CMOS or CCD based cameras will do for daytime viewing and both can be part of your system but during darkness CCD based cameras still offer clearer images.
The image device has varying sizes but 1/3 inch or 1/4 inch is generally available.
The larger the image sensor the wider the field of view a camera will have with the same lens.
The field of view of a 1/3" image sensor camera with a 3.6mm lens is 76 degrees horizontal, corner to corner.
The field of view of a smaller 1/4" image sensor camera with a 3.6mm lens decrease to 46 degrees horizontal.
Having a substantially narrower field of view you would require more cameras with a 1/4" image sensor to view the field of view obtained through a 1/3" image sensor.
Generally the larger image r will also provide a sharper image, lower light capability and better colour saturation when compared to an identical camera with a smaller size imager. Camera size is not related to the imager size.
Also dictates the field of view. They range from 2,5 mm to 18mm. The larger the lens the further it will clearly view but the narrower the field of view.
The wider the view required, the smaller the lens but the further away and therefore smaller the images in the field of view.
TV lines – Lines of resolution the camera provide and therefore the quality of video produced, the more lines the clearer the image. The clarity of view would depend on the quality lines of resolution that the monitor provide.
Colour
Black White
Standard
330 380
Medium
420 470
High
480 580
These days we have very good definition tv monitors so monitor clarity is not an issue any more.
Some cameras feature sensitive built in microphones which enable the viewer to hear sounds in the view area. This feature is useful and should be considered in the primary camera.
The professional standard is RG-59, 75 ohm, coaxial cable used for transmitting a video signal through copper wire. The wiring has a coaxial cross-section where an outer shielding protects the actual interior signal conductor from electromagnetic interference. For long runs RG-6 is used.
Wireless systems transferring video signals do exist and are getting better but due to external signal interference the quality viewing is not at this time comparable to wired systems. The better wireless systems are very costly. We concentrate on wired systems.
BNC a locking type of connector plug is used by video professionals. BNC plugs are easily adapted to standard consumer RCA connectors using a simple one-piece plug adapter.
Twin flex. Keep the DC power cable to the camera as short as possible as over a long wire run voltage drop is possible which cause image distortions.
Allow viewing from anywhere and a choice of hard disk storage sizes for recording. Also allows an alarm system where movement in the field of view of your setting, triggers off an alarm. Programming is embedded in the unit and operation is trouble free
Any TV will do and the system can be incorporated with your present TV setup.
Where possible ensure a light coloured background, light coloured walls instead of dark walls.
Cameras CCD or CMOS based
Colour
Infrared visibility from 15m - 30m
1/4 or a 1/3 Image Sensor
Lens 3,6mm or 2,8mm where a nearer and wider field of view is required.
a Very effective alarm system can be set up.